Standard Mechanical Interface Pods (SMIF pods) are in general comprised of a pod door which mates with a pod shell to provide a sealed environment in which wafers may be stored and transferred. One type of pod is a front opening unified pod, referred to as FOUP 10, in which the pod door is located in a vertical plane, and the wafers are supported either in a cassette mounted within the pod shell, or two shells mounted in the pod shell.
During the fabrication of semiconductor wafers, the SMIF pods are used to transport the workpieces between various tools in the wafer fab. These tools include process tools for forming integrated circuit patterns on the wafers, metrology tools for testing the wafers, sorters for sorting and rearranging the wafers within one or more SMIF pods, and stockers for large scale storage of SMIF pods. The tools are generally laid out in a wafer fab in one of two configurations, a bay and a chase configuration or a ballroom configuration. In the former arrangement, only the front of the tool including the workpiece I/O port is maintained in the clean room environment of Class-1 or better. In the ballroom configuration, the tools are arranged in clusters according to the operations they perform, with the entire tool being maintained in the clean room environment of Class-1 or better.
Tools within a wafer fab include a front-end interface which houses components that facilitate and monitor the transfer of workpieces (i.e. wafers) between the pods to the tools. A conventional front end unit or equipment front end module (EFEM) 20 is shown in FIGS. 1–2. EFEMs 20 are generally constructed at a tool manufacturer and then shipped to a wafer fab.
An EFEM 20 generally includes a housing 22 which is fixed to the front of the tool and a workpiece handling robot 24 mounted within the housing and is capable of x, r, θ, Z motion to transfer workpieces between the workpiece carriers, tool and other front end components. The robot 24 is generally mounted with leveling screws that will allow the adjustment of the planarity of the robot 24 once the EFEM 20 is constructed and affixed to a tool.
In addition to a robot 24, the EFEM 20 generally includes one or more prealigners 26 for performing the operation of wafer center identification, notch orientation, and indocile mark reading. The prealigner(s) 26 are commonly bolted into the housing 22 with leveling screws allowing the planarity of the prealigner(s) to be adjusted once the EFEM 20 is constructed and affixed to a tool.
An EFEM 20 further includes one or more load port assemblies 28 for receiving a workpiece carrier, opening the carrier, and presenting the workpiece to the robot 24 for transfer of the workpieces between the carrier, and other processing tools. For 300 mm wafer processing, a vertically oriented frame, commonly referred to as a Box Opener-Loader Tool Standard Interface (or “BOLTS” interface), has been developed by Semiconductor Equipment and Materials International (“SEMI”). The BOLTS interface attaches to, or is formed as part of, the front end of a tool, and provides standard mounting points for the load port assembly to attach to the tool. U.S. Pat. No. 6,138,721, entitled “Tilt and Go Load Port Interface Alignment System,” which is assigned to the owner of the present application and which is incorporated by reference in its entirety herein, discloses a system for adjusting a load port assembly to the proper position adjacent a BOLTS interface and then affixing the load port assembly to the interface.
Once the robot 24, the prealigners 26 and load port assemblies 28 have been mounted to the housing 22, the EFEM 20 is shipped to the wafer fab and affixed to a tool within the fab. After being properly secured to the tool, the EFEM components are leveled within the housing 22 via the leveling screws, and the robot 24 is then taught the acquisition and drop-off positions it will need to access for workpiece transfer between the load port assemblies, the prealigners and the tool. A system for teaching the various acquisition and drop-off positions for the robot within the tool front end is disclosed in U.S. patent application Ser. No. 09/729,463, entitled “Self Teaching Robot,” which application is assigned to the owner of the present application and which application is incorporated by reference herein in its entirety. Once the robot positions have been taught, side panels are attached to housing 22 to substantially seal the housing against the surrounding environment.
For example, conventional EFEMs include many separate and independent workpiece handling components mounted within an assembled housing. The housing 22 includes a structural frame, bolted, constructed or welded together, in a plurality of panels affixed to the frame. After the housing 22 is assembled, the EFEM components are fixed to the various panels. It is a disadvantage to prior art EFEMs that the overall system tolerances are compounded with each frame member, panel and component connection. The result is that the assembled EFEM components are poorly aligned and need to be adjusted to the proper position with respect to each other. The robot 24 must also be taught the relative positions of the components so that the EFEM components can interact with each other. This alignment and teaching process must take place every time there is an adjustment to one or more of the EFEM components.
A further shortcoming of the prior art is that EFEM components are frequently made by different suppliers, each with its own controller and communication protocols. Steps must be taken upon assembly of the EFEM so that the controllers of each component can communicate with each other and the components can interact with each other. The separate controllers also complicate maintenance and add to the parts and electrical connections provided in the EFEM. Further still, especially in a ballroom configuration, the conventional EFEM takes up a large amount of space within a Class-1 cleanroom environment where space is at a premium.
Today's 300 mm semiconductor EFEMs are comprised of several major subsystems including SEMI E15.1 compliant load port modules (typically 2–4 per tool). For example, an EFEM may consist of a wafer handling robot and a fan filter unit mounted to a structural steel frame, and have panels to enclose the wafer handling area between the load ports and the process tool. The combination of these components provides a means of transferring wafers to and from a FOUP 10, and between the FOUP and the process tool wafer dock(s). FOUPs 10 are manually loaded via operators or automatically loaded via an automated material handling system (AMHS) delivered to and taken from the Load Port. Industry Standards have been created to allow multiple vendors to provide the Load Port, FOUP 10, or other EFEM components to be integrated as a system.
The Load Port component provides a standard interface between the AMHS and the wafer handling robot in the EFEM. It provides a standardized location to set the FOUP 10, docks the FOUP 10 to seal the front surface, and opens and closes the door to allow access to the wafers in the FOUP 10. The dimensions of this unit are all specified in SEMI E15.1.
The Load Port attaches to the Front End via the Bolts Interface which is defined by SEMI E-63. This standard defines a surface and mounting holes to which the Load Port attaches. It is defined to start at the fab floor and goes as high as 1386 mm from the floor and is about 505 mm wide per Load Port. As a result, the load port completely blocks off the process tool from the operator aisle in the fab. SEMI E-63 also defines load port dimensions on the tool side to ensure interchangeability with a variety of robot manufacturers.
The primary functions of the load port include accepting aFOUP 10 from and presenting to a FOUP 10 to the Fab AMHS, moving the FOUP 10 towards and away from the port seal surface (docking/undocking), and opening and closing the FOUP door. In addition, it must perform functions such as locking the FOUP 10 to the advance plate, lock and unlock the FOUP door, and a variety of lot ID and communication functions. Per SEMI E15.1, all of these functions are contained in a single monolithic assembly which is typically added or removed from the tool front end as a complete unit.
The load port must be aligned with precision to the wafer robot. If there are multiple load ports in the system, they must all present the wafers in level parallel planes. Typically, the Load Ports provide several adjustments to planarize the wafer in the FOUP 10 with the robot. In order to minimize time spent calibrating the robot to each of the 25 wafer positions in each of the FOUPs 10, specialized tools and alignment fixtures are used in conjunction with all of the adjustments. If a load port is swapped out with a new one, the calibration procedure can be quite lengthy.
In addition to aligning the robot to the wafers positions, the door mechanism must also be aligned with the door opening and the door seal frame. Again, this is typically performed with alignment fixtures and tools either on the tool front end or off line.
The robot must also be leveled and aligned with one or more tool drop off point. This is typically done manually by teaching the robot the position and making planarity adjustments either on the front end or the tool.
It is the combination of all of these relationships between the tool, the robot, and the FOUPs 10 which make setting up a tool front end so time consuming. All of the components are typically attached to a relatively low precision frame, and adjustments are used to compensate for it. The load ports are mounted to the front surface, the robot to the base, the fan/filter unit (FFU) to the top, and skins on all other open surfaces to complete the mini-environment enclosure.
It would be advantageous to minimize the adjustments between the components and reduce the overall time required to align the load port. The present invention provides such an advantage.